[FFmpeg-devel] [PATCH 4/9] avformat/s337m: New ff_s337m_probe()

[Nicolas Gaullier]

Similar to ff_spdif_probe() with two additionnal parameters:
- an AVClass for logging
- the bit resolution of the container as it may be 16 or 24 for s337m
---
 libavformat/s337m.c | 35 +++++++++++++++++++++++++++++++++++
 libavformat/s337m.h | 19 +++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/libavformat/s337m.c b/libavformat/s337m.c
index 5c8ab2649c..dc62d6ab98 100644
--- a/libavformat/s337m.c
+++ b/libavformat/s337m.c
@@ -133,6 +133,41 @@ static int s337m_probe(const AVProbeData *p)
     return 0;
 }
 
+int ff_s337m_probe(const uint8_t *buf, int size, enum AVCodecID *codec, void *avc, int container_word_bits)
+{
+    int pos = 0;
+    int consecutive_codes = 0;
+
+    if ( size < S337M_MIN_OFFSET)
+        return 0;
+    size = FFMIN(2 * S337M_MAX_OFFSET, size);
+
+    do {
+        uint64_t state;
+        int data_type, data_size, offset;
+        while (pos < size - 12 && !buf[pos]) {
+            pos++;
+        }
+        if (pos >= size - 12 || pos < S337M_PROBE_GUARDBAND_MIN_BYTES)
+            return 0;
+        state = container_word_bits == 16 ? AV_RB32(buf + pos) : AV_RB48(buf + pos);
+        if (!IS_LE_MARKER(state))
+            return 0;
+        data_type = container_word_bits == 16 ? AV_RL16(buf + pos + 4) : AV_RL24(buf + pos + 6);
+        data_size = container_word_bits == 16 ? AV_RL16(buf + pos + 6) : AV_RL24(buf + pos + 9);
+        if (s337m_get_offset_and_codec(avc, state, data_type, data_size, container_word_bits, &offset, codec))
+            return 0;
+        if (avc) {
+            double s337m_phase = pos * 4. / container_word_bits / 48000;
+            av_log(avc, AV_LOG_INFO, "s337m sample %d detected with phase = %.6fs\n", consecutive_codes, s337m_phase);
+            if (*codec == AV_CODEC_ID_DOLBY_E && (s337m_phase < DOLBY_E_PHASE_MIN || s337m_phase > DOLBY_E_PHASE_MAX))
+                    av_log(avc, AV_LOG_WARNING, "Dolby E phase is out of valid range (%.6fs-%.6fs)\n", DOLBY_E_PHASE_MIN, DOLBY_E_PHASE_MAX);
+        }
+    } while (++consecutive_codes < 2);
+
+    return AVPROBE_SCORE_MAX;
+}
+
 static int s337m_read_header(AVFormatContext *s)
 {
     s->ctx_flags |= AVFMTCTX_NOHEADER;
diff --git a/libavformat/s337m.h b/libavformat/s337m.h
index d78ee8c501..707f982c9f 100644
--- a/libavformat/s337m.h
+++ b/libavformat/s337m.h
@@ -21,6 +21,25 @@
 #ifndef AVFORMAT_S337M_H
 #define AVFORMAT_S337M_H
 
+#define S337M_MIN_OFFSET 1601*4
+#define S337M_MAX_OFFSET 2002*6
+
+#define S337M_PROBE_GUARDBAND_MIN_BYTES     0
+#define DOLBY_E_PHASE_MIN       0.000610
+#define DOLBY_E_PHASE_MAX       0.001050
+
+/**
+ * Detect s337m packets in a PCM_S16LE/S24LE stereo stream
+ * Requires two samples with enough (S337M_PROBE_GUARDBAND_MIN_BYTES) and clean (set to zero) guard band
+ * @param p_buf Buffer
+ * @param size Buffer size
+ * @param codec Returns AV_CODEC_ID_DOLBY_E upon successful probing
+ * @param avc For av_log
+ * @param container_word_bits 16 or 24
+ * @return = AVPROBE_SCORE
+ */
+int ff_s337m_probe(const uint8_t *p_buf, int size, enum AVCodecID *codec, void *avc, int container_word_bits);
+
 /**
  * Read s337m packets in a PCM_S16LE/S24LE stereo stream
  * Returns the first inner packet found
-- 
2.14.1.windows.1